Range header of the HTTP protocol

First, lets start by seeing how the HTTP protocol allows downloads to be resumed. If you don’t already have PuTTY, get it from here. We will use PuTTY to directly connect to a HTTP server, send it some HTTP headers and see the response.

Create a text file with some text in it (at least 20 characters long to make it easier for us to test). Upload it so it is accessible at http://localhost/file.txt . I have used the URL http://localhost/file.txt . Change the settings below according to your URL. Open PuTTY and use the following settings:

Host Name: localhost
Port: 80
Connection Type: Raw
Close window on exit: Never

Click on Open. In the window that shows up, type the following:

GET /file.txt HTTP/1.1
Host: localhost
Range: bytes=5-
Connection: Close

Make sure you hit enter twice after typing the text above. You should see something like the text below if you had used something like “abcdefghijklmnopqrstuvwxyz” as the contents of file.txt:

HTTP/1.1 206 Partial Content
Date: Fri, 06 Nov 2009 16:25:07 GMT
Server: Apache/2.2.12 (Win32) mod_ssl/2.2.12 OpenSSL/0.9.8k
Last-Modified: Fri, 06 Nov 2009 15:56:25 GMT
ETag: "4000000044a82-1a-477b5e2d8093c"
Accept-Ranges: bytes
Content-Length: 21
Content-Range: bytes 5-25/26
Connection: close
Content-Type: text/plain

fghijklmnopqrstuvwxyz

You can see that it has returned a few headers followed by the contents of the file starting from the 6th byte. Try it a few more times modifying the Range header (for example, 5-15 to get bytes 6 to 16).

Using cURL to resume downloads

Resuming a download using cURL is quite straight forward. We use the CURLOPT_RANGE option to set the range if the file we are trying to download already exists and use the “a” option to fopen to append the contents to the file. The code is below:

$url="http://localhost/file.txt";
$fileName = "file.txt";

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);

if (file_exists($fileName)) {
	$from = filesize($fileName);
	curl_setopt($ch, CURLOPT_RANGE, $from . "-");
}

$fp = fopen($fileName, "a");
if (!$fp) {
	exit;
}
curl_setopt($ch, CURLOPT_FILE, $fp);
$result = curl_exec($ch);
curl_close($ch);

fclose($fp);

Using fsockopen to resume downloads

Resuming a download with fsockopen is more involved as it requires us to send the request headers and then parse the response headers:

$url="http://localhost/file.txt";
$fileName = "file.txt";

$partialContent = false;
$finalFileSize = 0;

$urlParts = parse_url($url);
$socketHandler = fsockopen($urlParts["host"], 80, $errno, $errstr, 30);
if (!$socketHandler) {
	exit;
} else {
	$from = 0;

	if (file_exists($fileName)) {
		$from = filesize($fileName);
	}

	$out = "GET " . $urlParts["path"] . " HTTP/1.1\r\n";
	$out .= "Host: " . $urlParts["host"] . "\r\n";
	$out .= "Range: bytes=" . $from . "-\r\n";
	$out .= "Connection: Close\r\n\r\n";

	$headerFound = false;

	if (!$fileHandler = fopen($fileName, "a")) {
		exit;
	}

	fwrite($socketHandler, $out);
	while (!feof($socketHandler)) {
		if ($headerFound) {
			if ($partialContent) {
				$result = fread($socketHandler, 8192);

				if (fwrite($fileHandler, $result) === false) {
					exit;
				}
			} else {
				fclose($fileHandler);
				fclose($socketHandler);
				exit;
			}
		} else {
			$result = fgets($socketHandler, 8192);
			$result = trim($result);
			if ($result === "") {
				$headerFound = true;
			}

			if (strstr($result, "206 Partial Content")) {
				$partialContent = true;
			}

			if (preg_match("/^Content-Range: bytes (\d+)-(\d+)\/(\d+)$/", $result, $matches)) {
				$finalFileSize = intval($matches[3]);
			}
		}
	}
	fclose($fileHandler);
	fclose($socketHandler);

	clearstatcache();

	if (filesize($fileName) == $finalFileSize) {
		// success
	} else {
		exit;
	}
}

Related posts:

1. cURL wrapper class with executable and PHP extension support
2. Domain name WHOIS query using PHP
3. Javascript and CSS compression using YUI compressor, PHP and gzip

Here’s the code:

/*
 * Takes a unix timestamp and returns a relative time string such as "3 minutes ago",
 *   "2 months from now", "1 year ago", etc
 * The detailLevel parameter indicates the amount of detail. The examples above are
 * with detail level 1. With detail level 2, the output might be like "3 minutes 20
 *   seconds ago", "2 years 1 month from now", etc.
 * With detail level 3, the output might be like "5 hours 3 minutes 20 seconds ago",
 *   "2 years 1 month 2 weeks from now", etc.
 */
function nicetime($timestamp, $detailLevel = 1) {

	$periods = array("second", "minute", "hour", "day", "week", "month", "year", "decade");
	$lengths = array("60", "60", "24", "7", "4.35", "12", "10");

	$now = time();

	// check validity of date
	if(empty($timestamp)) {
		return "Unknown time";
	}

	// is it future date or past date
	if($now > $timestamp) {
		$difference = $now - $timestamp;
		$tense = "ago";

	} else {
		$difference = $timestamp - $now;
		$tense = "from now";
	}

	if ($difference == 0) {
		return "1 second ago";
	}

	$remainders = array();

	for($j = 0; $j < count($lengths); $j++) {
		$remainders[$j] = floor(fmod($difference, $lengths[$j]));
		$difference = floor($difference / $lengths[$j]);
	}

	$difference = round($difference);

	$remainders[] = $difference;

	$string = "";

	for ($i = count($remainders) - 1; $i >= 0; $i--) {
		if ($remainders[$i]) {
			$string .= $remainders[$i] . " " . $periods[$i];

			if($remainders[$i] != 1) {
				$string .= "s";
			}

			$string .= " ";

			$detailLevel--;

			if ($detailLevel <= 0) {
				break;
			}
		}
	}

	return $string . $tense;

}

And some examples:

echo nicetime(time());

The result would be “1 second ago”

echo nicetime(time() - 839283);

The result would be “1 week ago”

echo nicetime(time() - 8392783);

The result would be “3 months ago”

echo nicetime(time() - 8392783, 3);

The result would be “3 months 1 week 6 days ago”

echo nicetime(time() - 83592783, 3);

The result would be “2 years 7 months 2 weeks ago”

echo nicetime(time() - 83592783, 5);

The result would be “2 years 7 months 2 weeks 1 day 12 hours ago”

echo nicetime(time() + 90532, 5);

The result would be “1 day 1 hour 8 minutes 52 seconds from now”

No related posts.

The PHP code is below:

class WhoisQuery {

	var $whoisServer;
	var $availableString;
	var $domainName;
	var $extension;

	function checkAvailability() {

		$output = "";

		if(($connection = @fsockopen($this->whoisServer, 43, $errno, $errstr, 15)) == false){
			return array("errno" => $errno, "errstr" => $errstr);
		}

		fputs($connection, $this->domainName . $this->extension . "\\r\\n");

		while(!feof($connection)) {
			$output .= fgets($connection, 4096);
		}

		fclose($connection);

		if (strlen($output) == 0) {
			return array("errno" => 0, "errstr" => "no output");
		}

		if ( is_integer( strpos($output, $this->availableString) ) ) {
			return true;
		} else {
			return false;
		}

	}

}

You can use it as shown below:

$domainAvailability = new WhoisQuery;
$domainAvailability->whoisServer = "whois.verisign-grs.com";
$domainAvailability->availableString = "No match for";
$domainAvailability->domainName = "ankur";
$domainAvailability->extension = ".com";

$result = $domainAvailability->checkAvailability();

if ($result === true) {
	echo "available";
} elseif ($result === false) {
	echo "not available";
} else {
	echo $result["errstr"];
}

We pass it the WHOIS server in whoisServer, the string that should be present in the response if the domain name is available in availableString, the first part of the domain name in domainName and the extension in extension. $result is an array with keys errno and errstr if an error occurred, true if the domain name is available and false if it isn’t.  Please note that WHOIS servers may limit the frequency of queries you perform. This has not been handled in the class.

You can connect to a WHOIS server manually using a program like PuTTY . Enter the WHOIS server name in the Host Name section and use the port 43. Type in the full domain name (example, ankur.com) and the response will be the WHOIS data.

Now, how do you find WHOIS servers for the extension you would like to check ? whois-servers.net provides some aliases for whois servers. For example, use com.whois-servers.net to connect to the .com WHOIS server. You can also check the IANA’s Database of Top Level Domains to see if it contains WHOIS server information for your extension.

Related posts:

1. Resume HTTP downloads in PHP using cURL or fsockopen
2. cURL wrapper class with executable and PHP extension support

Compressing javascript and CSS

The YUI Compressor allows you to easily reduce the size of javascript and CSS files by removing comments, extra white spaces, reducing the length of variables where applicable, etc from them. The result is a smaller sized file which works exactly like the original.

Compressing using the YUI Compressor is quite straight forward:

java -jar "yuicompressor-2.4.2.jar" --type js -o "file.compress.js" "file.js"
java -jar "yuicompressor-2.4.2.jar" --type css -o "file.compress.css" "file.css"

Here, file.compress.js and file.compress.css are the compressed output files and file.js and file.css are the input files. These compressed files will work exactly like the original ones. So, you can simple replace the originals with these new compressed files and immediately start seeing faster page load times.

Combining multiple files into one file

We have reduced the file sizes in the previous step. However, we might still have multiple javascript and CSS files required to completely load the page. This means the page has to make one HTTP request for each file it requires. Why not combine all the javascript files into one single .js file and all the CSS files into one single .css file ?

You can use any text editor and simple copy paste the contents into one javascript and CSS file. You will then need to modify your page to include these files instead of multiple javascript and CSS files.

Please note that this technique of combining files can end up requiring the user to download a large .js and .css file for each page if each page requires a different set of files. In that case, you might want to use this technique for only the core files that are required on each page or most pages.

Serve gziped files via PHP

Now that we have reduced the size and number of files considerably, we can further reduce the size by serving gzip content. If you use mod_gzip on apache, you might already be serving gziped files. However, you might still wish to use this section as compressing content on the fly with gzip might be slower than this technique.

We will first need to gzip the contents of the combined file from the previous step. Lets assume the file was file.js and the gzip compressed file is file.js.gz.

This file needs to be served through a PHP file. You can use the PHP code below to serve this file.

$longExpiryOffset = 315360000;
header ( "Cache-Control: public, max-age=" . $longExpiryOffset );
header ( "Expires: " . gmdate ( "D, d M Y H:i:s", time () + $longExpiryOffset ) . " GMT" );

header ( "Content-type: text/javascript; charset=utf-8" );

//Check if browser can handle gzip content
if (stripos ( $HTTP_SERVER_VARS ["HTTP_ACCEPT_ENCODING"], "gzip" ) === false) {
 readfile("file.js");
} else {
 header("Content-Encoding: gzip");
 readfile("file.js.gz");
}

Similarly, to serve CSS, replace text/javascript with text/css in line 5 and change the file names.

Of course, you will have to modify the HTML in your page to load this PHP script instead of the javascript and css files.

These steps should improve the page load time of your page considerably.

Related posts:

1. Resume HTTP downloads in PHP using cURL or fsockopen
2. cURL wrapper class with executable and PHP extension support

function hex2bin($hex) {

	return pack ( "H*", $hex );

}

class Cipher {

	public $password;

	public $plainText;

	public $encryptedText;

	public $iv;

	public $mode;

	const AES_128_ECB = "AES_128_ECB";

	const AES_128_CBC = "AES_128_CBC";

	public function __construct() {

		$this->mode = self::AES_128_ECB;

	}

	public function encrypt($useSuppliedIV = false) {

		if (!$this->plainText) {
			return "";
		}

		switch ($this->mode) {

			case self::AES_128_ECB :
			case self::AES_128_CBC :
				if (strlen($this->password) > 16) {
					$this->password = substr($this->password, 0, 16);
				}
				break;

		}

		if (function_exists ( "mcrypt_module_open" ) && function_exists ( "mcrypt_create_iv" ) && function_exists ( "mcrypt_generic_init" ) && function_exists ( "mcrypt_generic" ) && function_exists ( "mcrypt_generic_deinit" )) {

			switch ($this->mode) {

				case self::AES_128_ECB :
					$td = mcrypt_module_open ( 'rijndael-128', '', 'ecb', '' );
					break;

				case self::AES_128_CBC :
					$td = mcrypt_module_open ( 'rijndael-128', '', 'cbc', '' );
					break;

			}

			if ($useSuppliedIV) {
				if (strlen ( $this->iv ) != mcrypt_enc_get_iv_size ( $td )) {
					return null;
				}
			} else {
				$this->iv = mcrypt_create_iv ( mcrypt_enc_get_iv_size ( $td ), MCRYPT_RAND );
			}

			mcrypt_generic_init ( $td, $this->password, $this->iv );
			$this->encryptedText = mcrypt_generic ( $td, $this->plainText );
			mcrypt_generic_deinit ( $td );

		} else {

			$aes = new AES128 ( );
			$key = $aes->makeKey ( $this->password );

			$plainTextArray = str_split ( $this->plainText, 16 );

			$lastIndex = count($plainTextArray) - 1;
			if (strlen($plainTextArray[$lastIndex]) != 16) {

				for ($i = strlen($plainTextArray[$lastIndex]); $i < 16; $i++) {
					$plainTextArray[$lastIndex] .= chr (0);
				}

			}

			$this->encryptedText = "";

			if ($useSuppliedIV) {
				if (strlen ( $this->iv ) != 16) {
					return null;
				}
			} else {
				$this->iv = "";
				for ($i = 0; $i < 16; $i++) {
					$this->iv .= chr (rand(0, 255));
				}
			}

			switch ($this->mode) {

				case self::AES_128_ECB :

					for($i = 0; $i < count ( $plainTextArray ); $i ++) {
						$this->encryptedText .= $aes->blockEncrypt ( $plainTextArray [$i], $key );
					}

					break;

				case self::AES_128_CBC :
					$encryptedTextArray = array();
					for ($i = 0; $i < count ( $plainTextArray ); $i ++) {
						if ($i == 0) {
							$input = $this->iv ^ $plainTextArray[$i];
						} else {
							$input = $encryptedTextArray[$i - 1] ^ $plainTextArray[$i];
						}

						$encryptedTextArray[$i] = $aes->blockEncrypt ( $input, $key );
					}

					$this->encryptedText = join("", $encryptedTextArray);

					break;
			}
		}

	}

	public function decrypt() {
		if (!$this->encryptedText) {
			return "";
		}

		if (function_exists ( "mcrypt_module_open" ) && function_exists ( "mcrypt_create_iv" ) && function_exists ( "mcrypt_enc_get_iv_size" ) && function_exists ( "mcrypt_generic_init" ) && function_exists ( "mcrypt_generic" ) && function_exists ( "mcrypt_generic_deinit" )) {

			switch ($this->mode) {

				case self::AES_128_ECB :
					$td = mcrypt_module_open ( 'rijndael-128', '', 'ecb', '' );
					$this->iv = mcrypt_create_iv ( mcrypt_enc_get_iv_size ( $td ), MCRYPT_RAND );
					break;

				case self::AES_128_CBC :
					$td = mcrypt_module_open ( 'rijndael-128', '', 'cbc', '' );
					if (strlen ( $this->iv ) != mcrypt_enc_get_iv_size ( $td )) {
						return null;
					}
					break;

			}

			mcrypt_generic_init ( $td, $this->password, $this->iv );
			$this->plainText = mdecrypt_generic ( $td, $this->encryptedText );
			mcrypt_generic_deinit ( $td );

		} else {

			$aes = new AES128 ( );
			$key = $aes->makeKey ( $this->password );

			$encryptedTextArray = str_split ( bin2hex ( $this->encryptedText ), 32 );

			$this->plainText = "";

			switch ($this->mode) {

				case self::AES_128_ECB :
					for($i = 0; $i < count ( $encryptedTextArray ); $i ++) {
						$this->plainText .= $aes->blockDecrypt ( hex2bin ( $encryptedTextArray [$i] ), $key );
					}
					break;

				case self::AES_128_CBC :
					if (strlen ( $this->iv ) != 16) {
						return null;
					}

					$plainTextArray = array();
					for ($i = 0; $i < count ( $encryptedTextArray ); $i ++) {
						$output = $aes->blockDecrypt ( hex2bin($encryptedTextArray[$i]), $key );

						if ($i == 0) {
							$plainTextArray[$i] = $this->iv ^ $output;
						} else {
							$plainTextArray[$i] = hex2bin($encryptedTextArray[$i - 1]) ^ $output;
						}

						$this->plainText = join("", $plainTextArray);
					}
					break;

			}

		}

		$this->plainText = trim ( $this->plainText );

	}

}

Save the code above to cipher.php. In addition to this, you will need the AES128.php file from http://www.phpclasses.org/browse/package/3650.html

Here’s an example of AES-128 ECB mode encryption:

include_once ("AES128.php");
include_once ("cipher.php");

$encrypt = new Cipher;
$encrypt->password = "password";
$encrypt->plainText = "this is a very long string that we would like to encrypt using AES128";
$encrypt->encrypt();

echo "encrypted: " . bin2hex( $encrypt->encryptedText ) . "<br>";

$decrypt = new Cipher;
$decrypt->password = "password";
$decrypt->encryptedText = $encrypt->encryptedText;
$decrypt->decrypt();

echo "plain text: " . $decrypt->plainText;

The default mode is ECB. So, we don’t need to set $encrypt->mode and $decrypt->mode to Cipher::AES_128_ECB .

Here’s an example of AES-128 CBC mode encryption using an initialization vector:

include_once ("AES128.php");
include_once ("cipher.php");

$encrypt = new Cipher;
$encrypt->mode = Cipher::AES_128_CBC;
$encrypt->password = "password";
$encrypt->plainText = "this is a very long string that we would like to encrypt using AES128";
$encrypt->encrypt();

echo "iv: " . bin2hex( $encrypt->iv ) . "<br>";
echo "encrypted: " . bin2hex( $encrypt->encryptedText ) . "<br>";

$decrypt = new Cipher;
$decrypt->mode = Cipher::AES_128_CBC;
$decrypt->iv = $encrypt->iv;
$decrypt->password = "password";
$decrypt->encryptedText = $encrypt->encryptedText;
$decrypt->decrypt();

echo "plain text: " . $decrypt->plainText;

Related posts:

1. cURL wrapper class with executable and PHP extension support

The class I came up with is below:

class Curl {

	// Set to "PHP" or the path to the curl executable (binary)
	var $curlExecutable = "PHP";

	// URL to request, request type (GET or POST), request parameters as an associative array or null for none
	var $url;
	var $requestType = "GET";
	var $parameters = null;

	// request headers as an array
	var $requestHeaders = array();

	// certification authority, return data with headers, follow redirects and verify peer if URL is https
	var $cainfo = null;
	var $outputWithHeaders = false;
	var $followLocation = false;
	var $SSLVerifyPeer = true;

	// connect to remote server timeout and timeout to download the entire page
	var $connectTimeout = 30;
	var $timeout = 10800;

	// if there was an error, errorNumber and error is populated. data contains the page downloaded
	var $error = null;
	var $errorNumber = null;
	var $data = null;

	function fetchPage() {

		if ($this->curlExecutable == "PHP") {
			$ch = curl_init();

			if ($this->cainfo) {
				curl_setopt($ch, CURLOPT_CAINFO, $this->cainfo);
			}

			if ($this->SSLVerifyPeer) {
				curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, true);
			} else {
				curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
			}

			if ($this->requestType === "POST") {
				curl_setopt($ch, CURLOPT_POST, 1);

				if ($this->parameters) {
					if (is_array($this->parameters)) {

						$encodedParameters = "";
						$join = "";

						foreach ($this->parameters as $name => $value) {
							$encodedParameters = $encodedParameters . $join . rawurlencode($name) . "=" . rawurlencode($value);
							$join = "&";
						}

						curl_setopt($ch, CURLOPT_POSTFIELDS, $encodedParameters);

					} elseif (is_string($this->parameters)) {

						curl_setopt($ch, CURLOPT_POSTFIELDS, $this->parameters);

					}
				}

			} else {
				curl_setopt($ch, CURLOPT_POST, 0);

				if ($this->parameters) {
					$encodedParameters = "";
					$join = "?";

					foreach ($this->parameters as $name => $value) {
						$encodedParameters = $encodedParameters . $join . rawurlencode($name) . "=" . rawurlencode($value);
						$join = "&";
					}

					$this->url = $this->url . $encodedParameters;
				}

			}

			curl_setopt($ch, CURLOPT_HTTPHEADER, $this->requestHeaders);

			if ($this->outputWithHeaders) {
				curl_setopt($ch, CURLOPT_HEADER, 1);
			} else {
				curl_setopt($ch, CURLOPT_HEADER, 0);
			}

			if ($this->followLocation) {
				curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 1);
			} else {
				curl_setopt($ch, CURLOPT_FOLLOWLOCATION, 0);
			}

			curl_setopt($ch, CURLOPT_URL, $this->url);
			curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

			curl_setopt($ch, CURLOPT_CONNECTTIMEOUT, $this->connectTimeout);
			curl_setopt($ch, CURLOPT_TIMEOUT, $this->timeout);

			$this->data = curl_exec($ch);
			$this->error = curl_error($ch);
			$this->errorNumber = curl_errno($ch);
			curl_close($ch);

			if ($this->error) {
				return false;
			} else {
				return true;
			}

		} else {

			$command = $this->executable;

			$command = $command . " -s -S";

			$command = $command . " --connect-timeout " . $this->connectTimeout;
			$command = $command . " --max-time " . $this->timeout;

			if ($this->cainfo) {
				$command = $command . " --cacert \"" . $this->cainfo . "\"";
			}

			if ($this->outputWithHeaders) {
				$command = $command . " -i";
			}

			if ($this->followLocation) {
				$command = $command . " -L";
			}

			for ($i = 0; $i < count($this->requestHeaders); $i++) {
				$command = $command . " -H \"" . $this->requestHeaders[$i] . "\"";
			}

			if ($this->parameters){
				$encodedParameters = "";
				$join = "";

				foreach ($this->parameters as $name => $value) {
					$encodedParameters = $encodedParameters . $join . rawurlencode($name) . "=" . rawurlencode($value);
					$join = "&";
				}

				$command = $command . " -d " . escapeshellarg($encodedParameters) . "";
			}

			if ($this->requestType === "GET") {
				$command = $command . " -G";
			}

			$command = $command . " " . $this->url;

			$descriptorspec = array(
			0 => array("pipe", "r"),
			1 => array("pipe", "w"),
			2 => array("pipe", "w")
			);

			$process = proc_open($command, $descriptorspec, $pipes);

			if (is_resource($process)) {

				fclose($pipes[0]);    // close stdin as we are not going to supply any input

				$this->data = stream_get_contents($pipes[1]);    // read stdout
				$this->error = stream_get_contents($pipes[2]);    // read stderr

				fclose($pipes[1]);
				fclose($pipes[2]);

				$this->errorNumber = proc_close($process);

			} else {

				return false;

			}

			if ($this->errorNumber === 0) {
				return true;
			} else {
				return false;
			}

		}

	}

}

The following example fetches http://www.google.com :

$request = new Curl;
$request->curlExecutable = "PHP";
$request->followLocation = true;
$request->url = "http://www.google.com";
if ( $request->fetchPage() ) {
	header("Content-Type:text/plain");
	echo $request->data;
} else {
	echo "An error occured: " . $request->errorNumber . " - " . $request->error;
}

This example fetches a random quote (the ones tou see on the top right of this website):

$request = new Curl;
$request->curlExecutable = "PHP";
$request->url = "http://www.ankur.com/quotes.php";
$request->requestType = "GET";
$request->parameters = array(
	"action" => "random"
);
if ( $request->fetchPage() ) {
	header("Content-Type:text/plain");
	echo $request->data;
} else {
	echo "An error occured: " . $request->errorNumber . " - " . $request->error;
}

Unrelated to the cURL wrapper class, you can try changing the action parameter from random to all to fetch all the quotes.

Related posts:

1. AES wrapper class with pure php and MCrypt extension support
2. Resume HTTP downloads in PHP using cURL or fsockopen

A few demos of the library in action:

Scroll Demo

Full Demo

Cone Demo

You will find more information and detailed documentation at the Amazing Tree page

Related posts:

1. Frame Glider javascript library

Some demos are available too:

Simple Demo

Complex Demo

Frame as a droppable

More details including detailed documentation are available at the Frame Glider page

Related posts:

1. Amazing Tree javascript library
2. Javascript and CSS compression using YUI compressor, PHP and gzip